I think trying out radio navigation techniques in the comfort of your own home is an excellent learning aid. It is obviously much cheaper than a real lesson and more valuable than just drawing lines and little aeroplanes on a map.
Whilst there are lots of improvements overall, from memory there is not much that the latest Microsoft flight simulator (2002) adds to the 1998 version in the area of learning about radio nav. If you want a more realistic flight model (in my opinion) try X-Plane, another simulator.
However, better than a flight simulator, at least in the early stages, is this online nav simulation:
http://www.visi.com/~mim/nav/. This allows you to experiment with various navaids (ADF, VOR, RMI, HSI) using two beacons, effect of wind, etc. It is even better when it comes to the more advanced topics (not required for your PPL) like intercepting a radial from an NDB when flying outbound from on it in strong wind.